1. Field of the Invention
The present invention relates to electrolytic cells for the recovery of metals from solutions containing metal ions, particularly photographic processing solutions containing silver ions.
2. The Prior Art
In general, recovery cells of the above type comprise a container for the solution containing metal ions which forms the electrolyte. A pair (or pairs) of electrodes is located in the container in such a position as to be immersed in the electrolyte in use. One of the electrodes is arranged to be the cathode and the other is arranged to be the anode of the cell.
In use, a D.C. potential from a suitable source is applied across the electrodes and the metal ions are caused to migrate to the cathode where they are discharged and converted to metal atoms which generally adhere to the cathode. When sufficient metal has deposited on the cathode it is usually taken from the cell and the deposit removed therefrom, after which the cathode is replaced in the cell. The cell may be arranged to operate in a batchwise manner in which case electrolysis is continued until the concentration of metal ions in the cell is depleted down to a predetermined level, at which point the electrolysis is discontinued and the depleted solution replaced by a fresh solution. Alternatively, the cell may be arranged to operate in a continuous manner in which case the electrolyte is continually passed through the cell from an inlet to an outlet at a predetermined rate. The rate of passage of the electrolyte through the cell is such that a satisfactory proportion of the metal ions in the solution are discharged and converted to metal atoms at the cathode.
Prior art metal recovery cells require that the metal be recovered from the cathode of such cells by expensive and complicated chemical or mechanical means. Furthermore, in cells using planar cathodes the recovered metal would sometimes flake off, causing a short circuit.
The instant invention has solved the above problems of prior art metal recovery cells, by providing a cell in which the metal can be removed from the cathode of the cell by the simple process of combustion. An auxiliary advantage of the invention is that the recovered metal forms a granular deposit on the cathode of the cell, so that short circuits due to flaking are not likely to occur.